It ain't gonna work, because the bottom of the bores is closer to the crank CL on a B engine.

Feel free to grind the crank, attempt to drop it in and see if it will rotate, to see what is happening.
That is what I did, and right after that I cut the CW to 7.25 OD.

A tiny bit more material needed to be removed for balancing
with typical 1.32 CH forged shelf pistons.